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Can COVID Cause Brain Fog and Cognitive Deficits?

A new study suggests COVID may cause cognitive deficits for some.

Key points

  • In one study, some survivors of COVID showed deficits in immediate memory, visual search tasks, and cognitive reasoning.
  • In the most serious cases, researchers claim that cognitive performance of those with "long COVID" is akin to a 7-point IQ drop.
  • To minimize risk of cognitive declines due to COVID, the only current option is to avoid contracting the virus altogether.

Do you have COVID on your mind? Do you worry you have COVID in your mind or brain? Some people have reported severe brain fog after recovering from COVID. They are experiencing memory and other cognitive problems.

Can COVID cause long-term cognitive deficits? New evidence may provide the best investigation so far into the long-term effects of COVID on memory and thinking.


Do you know anyone who has recovered from COVID? Given the number of cases here in the US and around the world, most likely you do. Many people have bounced back quickly — they had a mild infection and quickly returned to normal. But others report ongoing problems.

What types of ongoing problems have they reported? Long COVID, as people call it, may leave people with a variety of negative effects, which include ongoing breathing problems, heart issues, digestive problems, sleep disruptions, muscle pain, and mood changes. The CDC is tracking and provides a summary of the type of ongoing problems many people are continuing to experience. And a New York Times article reported on the hundreds of thousands of people who have continued to suffer and sometimes started experiencing new symptoms as part of long COVID. In the research, nearly one-quarter of people who have recovered from COVID eventually report new symptoms later (by FAIR Health). This is a nasty virus. It leads to long-term consequences for many people.

And there appear to be brain and cognitive deficits that appear as a result of having had COVID — even after someone has recovered. In the study described in The New York Times, people often reported cognitive problems — describing an overall brain fog. Nature News reported that COVID is causing ongoing cognitive problems, including memory loss, confusion, and difficulties tracking things.

A New Study of COVID and Cognitive Deficits

A new investigation provides the clearest evidence yet that many people are experiencing serious cognitive declines following COVID. Even in people who have recovered, or had few symptoms, there is evidence of long-lasting cognitive declines.

Hampshire et al. (2021) have collected performance on a set of cognitive measures from over 80,000 people, of whom over 12,000 reported they had COVID. They got this data as part of a project in the United Kingdom with the BBC: The Great British Intelligence Test. The set of tests were promoted on the BBC and people were encouraged to take this simple assessment. Originally, the goal was to give people feedback on their strengths — the areas in which they performed best. But after COVID began to spread, the research team started asking additional questions about whether people had been infected and also the severity of their COVID infection.

What type of cognitive tasks were tested? Some were measures of immediate memory capacity and visual search. Others required more challenging reasoning skills. When looking overall, Hampshire and colleagues found substantial effects of COVID. The more severe someone’s case was, the larger the cognitive declines. For people with more severe COVID, these weren't small deficits. But even milder cases, when someone recovered at home without additional medical care, resulted in reliable deficits. The effects were stronger in the more challenging cognitive tasks. They appeared in the immediate memory and visual search tasks, but they were stronger in the cognitive reasoning tasks. COVID brain fog is real.

The COVID Cognitive Deficits Are Substantial

These effects are really large. Hampshire and colleagues note that in serious cases, this would be around a 7-point loss in an IQ measurement. They stated that it was equal to the amount of decline typically seen as people age.

Although the effects are correlational, Hampshire and colleagues attempted to rule out other possible causes. They controlled for age, education, and overall mood. But the effects of COVID remained. Did time since someone had COVID matter? Maybe it just takes time to fully recover? But it appears that time wasn’t important. The effects remain over several months.

This really worries me. People with long COVID may have cognitive deficits that persist for months and perhaps years. This should certainly play into your assessment of the risk of catching COVID. Maybe you’ll be fine. On the other hand, do you want to risk long-term cognitive deficits?

Avoiding Cognitive Deficits by Avoiding COVID

But there’s good news if you are worried about COVID causing cognitive deficits. Do your part to avoid catching COVID. Of course, that means getting vaccinated if you aren’t already. It also means continuing to use other public health measures such as masking until COVID is completely eliminated.

At this point, people are just beginning to study long COVID, including the cognitive deficits that COVID appears to cause. Over time, perhaps people will completely recover. Eventually, there may be treatments. Hopefully, in a few years, I will be writing about treatments for the cognitive declines caused by COVID. But for now, the best approach is to avoid catching COVID in the first place. COVID is a nasty disease. For me, the issues associated with long COVID are a serious reason to get vaccinated.


Hampshire, A., Trender, W., Chamberlain, S. R., Jolly, A. E., Grant, J. E., Patrick, F., ... & Mehta, M. A. (2021). Cognitive deficits in people who have recovered from COVID-19. EClinicalMedicine, 101044.